Question

Define case control study and cohort study.

Hint:

Case-control studies are often used to investigate rare diseases, while cohort studies are better for studying common outcomes and establishing causality.

Answer 1

Case-control and cohort studies are both types of observational research designs used to study associations between exposures and outcomes.
Step 1: Case-Control Study:
- In a case-control study, participants are selected based on the outcome they have experienced (the "cases") or not experienced (the "controls"). Researchers then look backward in time to determine the exposure or risk factors that may have contributed to the outcome.
- This type of study is useful for studying rare diseases or outcomes.
- Example: A study investigating the association between smoking and lung cancer would select people with lung cancer (cases) and people without lung cancer (controls) and then compare their smoking histories.
Step 2: Cohort Study:
- In a cohort study, participants are selected based on their exposure to a potential risk factor and then followed over time to observe the occurrence of outcomes (such as disease or death). Cohort studies can be prospective (looking forward) or retrospective (looking back).
- This type of study is useful for studying common diseases or outcomes and establishing the temporal relationship between exposure and outcome.
- Example: A cohort study might follow a group of smokers and a group of non-smokers over several years to observe the development of lung cancer.